1. Field of the Invention
The present invention relates to a technological field of an image change detecting apparatus and an image change detecting method, an image encoding apparatus and an information recording medium with an image change detecting program recorded readable by a computer. More specifically, it relates to a technological field of an image change detecting apparatus and an image change detecting method for detecting whether or not there occurs an image change (in general, referred to as a scene change), which takes place between two consecutive frame images as remarkable difference in image information amount included therein, an image encoding apparatus including the same, and an information recording medium with the image change detecting program recorded readable by a computer.
2. Description of the Related Art
In general, in the case of encoding (including compression encoding) of moving picture information comprising a plurality of frame images, the encoding parameter should be controlled optimally according to the characteristics of the moving picture information.
Here, as a method recently used commonly for the above-mentioned encoding method, the so-called MPEG (moving picture experts group) method can be presented.
This MPEG method is a kind of an encoding process using the so-called discrete cosine transform (DCT) method. These days, it is the international standard for high efficiency encoding (compression encoding) of the image information (including both moving picture information and still picture information).
In compression encoding of an image by the MPEG method, in general, an original image to be applied with compression encoding is divided into blocks called macro blocks as pixel blocks (including pixels comprising the original image by 16 pixelsxc3x9716 pixels) so that movement compensation, the above-mentioned DCT, or a process such as binarization is carried out by the macro block unit.
In optimizing the movement compensation, the DCT, and the like at the time of encoding, in particular, the moving picture information, it is standardized in the MPEG method that the optimization is carried out by changing the parameter at the time of encoding (specifically, the quantization scale, the movement vector, or the like) with the in-frame distribution value per the above-mentioned macro block unit, or the like in the moving picture information to be encoded, provided as the key.
Here, the above-mentioned in-frame distribution value is the difference between the luminance in each pixel included in a frame image and the average value of the luminance in the frame image, in other words, the value representing to which extent the irregularity (distribution) of the luminance exists in each pixel in the frame image. That is, with a high in-frame distribution value, a frame image with full of variety as to the luminance is provided. In contrast, with a low in-frame distribution value, a monotonous frame image without variety is provided.
On the other hand, a so-called scene change in which there is a remarkable difference between two consecutive frame images in image information included therein may be included occasionally in the above-mentioned moving picture information to be encoded. In this case, the scene change corresponds visibly to the case of, for example, instantaneous change of the camera angle from an image including only the sky to an image including the woods.
At the time, among the above-mentioned scene changes, particularly in the case of a scene change from an image with a complicated configuration to an image with a monotonous configuration, it is necessary to detect the timing of the scene change, and set the parameter suited for the monotonous image after the detection of the timing. In the case the monotonous image is encoded with the parameter suited for the high compression for the complicated image maintained without the setting, a process for decoding the encoded moving picture for reproduction thereof causes problems that various noises may be included in the reproduced moving picture to the corresponding period immediately after the scene change.
In this regard, as a method for detecting the scene change in the conventional MPEG method, the in-frame distribution value in each frame image is always monitored for detecting whether or not the scene change occurs based on the change of the in-frame distribution values in two consecutive frame images (such a conventional scene change detecting method is disclosed for example, in Japanese Patent Application Laid-Open (JP-A) No. 11-242747 in detail.).
However, according to the conventional scene change detecting method, whether or not occurrence of the scene change is detected only in terms of the in-frame distribution value change. As a result, a scene change (that is, a scene change with a in-frame distribution value showing a change of more than a threshold value for a preset scene change detection but without the need of changing an encoding parameter (more specifically, the case of changing the camera angle from an image of a monotonous green woods to an image of a complicated green woods, or the like)) other than a scene change necessary in encoding (in other words, a scene change with the need of changing an encoding parameter) is also detected. As a result, the encoding parameter can be changed at a timing without the need of the change. In this case, the encoding efficiency is lowered so that effective encoding is disabled, and thus it is problematic.
Accordingly, in order to solve the above-mentioned problems, an object of the present invention is to provide an image change detecting apparatus and an image change detecting method capable of detecting only a necessary scene change in encoding by the MPEG method accurately and certainly, an image encoding apparatus including the same, and an information recording medium with the image change detecting program recorded readable by a computer.
In order to solve the above-mentioned problems, a first aspect of the present invention provides an image change detecting apparatus for detecting occurrence of an image change which takes place between two consecutive frame images as difference in image information amount included therein in moving picture information having a plurality of frame images, comprising: a distribution value detecting device for detecting each in-frame distribution value of the frame images, an absolute value sum detecting device for detecting each predicted error absolute value sum of the frame images, and an image change detecting device for detecting whether or not the image change takes place between the two frame images based on change between the in-frame distribution values of the two consecutive frame images and on change of the predicted error absolute value sums at boundary timing of the frame images.
Therefore, since whether or not occurrence of the image change is detected based on the change in the in-frame distribution values between two consecutive frame images and the change of the predicted error absolute value sums at the boundary timing, the image change influencing encoding can be detected certainly and accurately.
Accordingly, since the image change in the moving picture information can be detected certainly and accurately, an image process of encoding with the encoding parameter changed at the image change timing, or the like can be carried out.
In order to solve the above-mentioned problems, a second aspect of the present invention provides the image change detecting apparatus according to the first aspect, wherein the image change detecting device judges that the image change takes place between the two consecutive frame images when the in-frame distribution values of the frame images are larger than a preset value as well as the predicted error absolute value sums have an extreme value at the boundary timing of the two frame images.
Accordingly, since a judgement is made that the image change takes place between the two consecutive frame images when the in-frame distribution values of each of the frame images are larger than a set value as well as the predicted error absolute value sums have an extreme value at the boundary timing thereof, the image change can be detected further certainly and accurately.
In order to solve the above-mentioned problems, a third aspect of the present invention provides the image change detecting apparatus according to the second aspect, wherein the image change detecting device judges that the image change due to reduction in information amount takes place between the two consecutive frame images when the in-frame distribution value of a prior one of the frame images is larger than the in-frame distribution value of a latter one of the frame images.
Accordingly, the image change with the information amount reduced between the two consecutive images can be detected further certainly and accurately.
In order to solve the above-mentioned problems, a fourth aspect of the present invention provides the image change detecting apparatus according to the second aspect, wherein the image change detecting device judges that the image change due to increase in information amount takes place between the two consecutive frame images when the in-frame distribution value of a prior one of the frame images is smaller than the in-frame distribution value of the latter one of the frame images.
Accordingly, the image change with the information amount increased between the two consecutive images can be detected further certainly and accurately.
In order to solve the above-mentioned problems, a fifth aspect of the present invention provides an image encoding apparatus comprising: the image change detecting apparatus according to any one of first to fourth aspects, and an encoding device for encoding moving picture by changing an encoding parameter for encoding the moving picture information after occurrence of the image change is detected.
Accordingly, since the image change is detected certainly and the encoding parameter is changed at the image change timing, the moving picture information can be encoded further accurately with the noises reduced.
In order to solve the above-mentioned problems, a sixth aspect of the present invention provides an image change detecting method for detecting occurrence of an image change which takes place between two consecutive frame images as difference in image information amount included therein in moving picture information having a plurality of frame images, comprising: a distribution value detecting process for detecting each in-frame distribution value in the frame images, an absolute value sum detecting process for detecting each predicted error absolute value sum of the frame images, and an image change detecting process for detecting whether or not the image change takes place between the two frame images based on change between the in-frame distribution values of the two consecutive frame images and on change of the predicted error absolute value sums at boundary timing of the frame images.
Therefore, since whether or not occurrence of the image change is detected based on the change of the in-frame distribution values between two consecutive frame images and the change of the predicted error absolute value sums at the boundary timing, the image change influencing encoding can be detected certainly and accurately.
Accordingly, since the image change in the moving picture information can be detected certainly and accurately, an image process of encoding with the encoding parameter changed at the image change timing, or the like can be carried out.
In order to solve the above-mentioned problems, a seventh aspect of the present invention provides the image change detecting method according to the sixth aspect, wherein the image change detecting process judges that the image change takes place between the two consecutive frame images when the in-frame distribution values of the frame images are larger than a preset value as well as the predicted error absolute value sums have an extreme value at the boundary timing of the two frame images.
Accordingly, since generation of the image change between the two consecutive frame images is detected when the in-frame distribution values of each of the frame images are larger than a set value as well as the predicted error absolute value sums have an extreme value at the boundary timing thereof, the image change can be detected further certainly and accurately.
In order to solve the above-mentioned problems, an eighth aspect of the present invention provides an information recording medium with an image change detecting program recorded readable by a computer, wherein the program causes the computer, which is included in an image change detecting apparatus for detecting occurrence of an image change which takes place between two consecutive frame images as difference in image information amount included therein in moving picture information having a plurality of frame images, to function as: a distribution value detecting device for detecting each in-frame distribution value of the frame images; an absolute value sum detecting device for detecting each predicted error absolute value sum of the frame images; and an image change detecting device for detecting whether or not the image change takes place between the two frame images based on change between the in-frame distribution values of the two consecutive frame images and on change of the predicted error absolute value sums at boundary timing of the frame images.
Therefore, since the computer functions so as to detect whether or not the image change occurs based on the change of the in-frame distribution values between two consecutive frame images and the change of the predicted error absolute value sums at the boundary timing, the image change influencing encoding can be detected certainly and accurately.
Accordingly, since the image change in the moving picture information can be detected certainly and accurately, an image process of encoding with the encoding parameter changed at the image change timing, or the like can be carried out.
In order to solve the above-mentioned problems, a ninth aspect of the present invention provides the information recording medium with the image change detecting program recorded according to the eighth aspect, wherein the program causes the computer functioning as the image change detecting device to function to make a judgement that the image change takes place between the two consecutive frame images when the in-frame distribution values of the frame images are larger than a preset value as well as the predicted error absolute value sums have an extreme value at the boundary timing of the two frame images.
Accordingly, since the computer functions so as to detect generation of the image change between the two consecutive frame images when the in-frame distribution values of each of the frame images are larger than a set value as well as the predicted error absolute value sums have an extreme value at the boundary timing thereof, the image change can be detected further certainly and accurately.